The dramatic increase in HIV/AIDS incidence in Russia in 1999-2001 has been largely attributed to transmission through unsafe injecting practices among intravenous drug users. However, given the nature of surveillance, screening and epidemiological methods in Russia, little is known about the HIV prevalence, risk behaviors or the possibly important interactions of persons at risk for both sexual and parenteral acquisition and transmission of HIV and other pathogens. Sex workers represent a particularly vulnerable group in Russia; there is mounting evidence that these women are involved in the recent epidemics of STIs and use of injection drugs in Russia. This research proposal is a novel collaboration between AIDS infoshare Russia, a long-standing Russian Non-Governmental Organization (NGO) that works with sex workers; the Russian National Institute of Dermatovenerology; the lvanovsky Institute of Virology of Moscow University; and the Departments of Epidemiology and International Health of Johns Hopkins University School of Public Health. Formative research will be conducted among sex workers and key informants, followed by quantitative research of KAPB, and studies of prevalence and incidence of HIV, hepatitis C and sexually transmitted diseases. The feasibility of recruiting and retaining a cohort of sex workers will be assessed over a 12-month period. Until now, sex workers have remained an underserved and unstudied population. The primary goal of this project is to illuminate and address a public health emergency by combining the rare trust and access to these vulnerable women and girls earned by Russian NGOs, with the expertise of Russian and US scientific institutions.